Recently, prolonged exposure in vivo (flooding) has been demonstrated as an effective behavioral treatment for agoraphobia, but its overall clinical effectiveness remains unclear because of an exaggerated reliance on the statistical rather than the clinical significance in most of the studies, and also because the drop out rate is high and follow-up studies are rare. Similarly, antidepressants (imipramine) have also been shown to be effective pharmacological treatment for this syndrome. However, relapse rate is extremely high upon withdrawal of the drugs. The literature suggests that imipramine suppresses the present panic attacks of the agoraphobic patients, and that exposure in vivo is necessary to diminish phobic anxiety and avoidance behavior. It is impossible to estimate and compare the outcome of these two treatments due to the vastly different methods of assessment employed by various investigators, and because the few studies comparing behavior therapy and pharmacotherapy and their combination have not chosen flooding as their behavioral treatment. In this proposal, the effectiveness of flooding and imipramine as well as their combined treatments will be assessed in 80 chronic agoraphobics using a two-by-two factorial design. Four groups of 20 patients each will participate: Group 1 will receive imipramine, 90 minute weekly group flooding sessions and weekly individual 15 minute sessions. Group 2 will receive imipramine, 90 minute weekly group discussion and weekly individual 15 minute sessions. Group 3 will receive placebo, 90 minute weekly group flooding sessions and 15 minute weekly individual sessions. Group 4 will recieve placebo, 90 minute weekly group discussion and 15 minute weekly individual sessions. The differential response of symptoms and clinical improvement and the rapidity with which change occurs and is maintained will be investigated with repeated multiple clinically relevant measures in behavioral, physiological and self-report response systems. It is expected that the addition of imipramine or flooding to non-specific therapeutic factors (control group 4) will increase the effectiveness of the treatment, and that results with combination treatment will be superior to those obtained with single treatments.